Polyolefins are a class of polymers derived from simple olefins. Known methods of making polyolefins involve the use of Ziegler-Natta polymerization catalysts. These catalysts polymerize vinyl monomers using a transition metal halide to provide a stereoregulated polymer.
Numerous Ziegler-Natta polymerization catalysts exist. The catalysts have different characteristics and/or lead to the production of polyolefins having diverse properties. For example, certain catalysts have high activity while other catalysts have low activity, and similarly certain catalysts have a long life while other catalysts have a short life. Moreover, polyolefins made with the use of Ziegler-Natta polymerization catalysts vary in stereoregularity, molecular weight distribution, impact strength, melt-flowability, rigidity, heat sealability, isotacticity, and the like.
Useful Ziegler-Natta polymerization catalysts made through a precipitation method are made using an organic magnesium compound starting material. The organic magnesium compound leads to the formation of a desirable spherical catalyst particle. Replacing the organic magnesium compound starting material with a markedly less expensive magnesium halide results in a catalyst particle with a morphology that is difficult to control and aspherical or the use of expensive capital processes such as spray congealing (processes where MgCl2 is mixed with ethanol, heated to form a meld, and then sprayed through a nozzle into a cold liquid or gas).